1. Define the available animation clips at the object level, and set up the crowd network at the geometry level (SOP network). The Agent SOP, Agent Clip SOP, and Agent Transform Group SOP make up the agent definition:

   

2. Create the agent using an Agent SOP:

   • Set the Character Rig parameter to the node that contains the character rig with the base animation. You can use the button on the right of the parameter to choose from the window that pops up. In our example, we set Character Rig to ../../mocapbiped3_walk.

3. Add the base (walking) animation clip to the agent definition using an Agent Clip SOP:

   • In the Clips set of parameters, set Name to walk.

   • Set Character Rig to ../../mocapbiped3_walk.

4. We want the agent to keep moving forward while looping the walking clip, so on the Agent Clip SOP:

   • Set Locomotion Node to the joint that has the agent’s overall translation and moves it forward in space. For a biped, this is usually the hip joint.

   • Delete the channels on Start/End/Inc - Start/End/Inc and select Delete Channels.

   • On Start/End/Inc, set the start and end frames of the walking clip.

   • Turn on Convert to In-Place Animation.

   Note

   To preview the clip:

   1. Turn on Set Current Clip and set the parameter to walk.

   2. Turn on Apply Clip Locomotion to see the agent’s position keep moving forward over time while the clip loops. To see the agent walk in place, turn off Apply Clip Locomotion.

5. Add the layered (clapping) animation clip to the agent definition using the same Agent Clip SOP:

   • Click beside Clips to add another set of clip parameters.

   • Set Name to clap.

   • Set Character Rig to ../../mocapbiped3_clap.

6. The Agent Transform Group SOP creates a named group of joints that specifies the parts of the skeleton to apply the layered clip to. Place the Agent Transform Group SOP anywhere in the agent definition after the Agent SOP and before the Crowd Source SOP:

   • Use the Transform Groups multiparm to create new joint groups. Specify a name for the joint group in the Name parameter, in our example, upper_body.

   • In Root Transforms, select the root joint(s) for the group. Each root joint and its descendants are added to the group. In our example, we set Root Transforms to Spine_To_Spine1. To see the joints that are part of the group, turn on Show Guide Geometry, which displays spheres around the selected joints. Display the agent as Wireframe to more clearly see the guide geometry:

     

7. On the Crowd Source SOP, set the Initial State parameter to one of the available states in the DOP network. The states are specified in the Crowd State DOP’s State Name parameter. In our DOP network, there is a walk state, so we set Initial State to walk.

8. Set up the DOP simulation network.

The image below displays the DOP network, crowd_simulation, from the parent SOP network:

1. Connect the following inputs to the crowdsolver DOP:

   • The crowdobject DOP to the 1st input (Crowd Object input) of the crowdsolver DOP.

   • The crowd states to the 3rd input (States input) of the crowdsolver DOP.

   Note

   The Agent Clip Layer DOP can also be placed after merging the states and before the crowd solver.

2. On the crowdobject DOP, set Source to First Context Geometry because the Crowd Source SOP in the parent SOP network is connected to the first input of the crowd_simulation DOP network node.

3. On the Crowd State DOP, set up the crowd state that plays the base animation clip:

   • Rename the Crowd State DOP to the name of the base animation clip, walk.

     Note

     By default, Clip Name is set to $OS, which sets the animation clip that the state plays to the name of the Crowd State DOP.

   • Set Type to Locomotive because the original walking clip had some overall root motion.

4. On the Crowd Trigger DOP, set the trigger that activates the layered clip:

   • Set Type to Object Bounds.

   • Set Object SOP Path to the bounding box, in our example, ../../../box.

   • Set Check to Continuous so that the layered clip is triggered as long as the agent is inside the bounding box.

5. On the Agent Clip Layer DOP, set the clapping animation clip to layer on top of the skeleton:

   • By default, the Blend Mode is set to Interpolate, so an interpolation is performed between the base animation and layered clip depending on the value of the Blend Ratio.

     Note

     To instead add the effect of the layered animation on top of the base animation, see additive layers for more information.

   • Set Clip Name to clap. This is the clip to layer on top of the base animation.

   • Set Transform Group to upper_body. This is the group of joints that plays the layered animation.

   • Adjust the Blend Ratio to control the blend between the layer and base animation.

   • Turn on Activate with Trigger. The Crowd Trigger DOP is connected to the 1st trigger input (2nd input) of the Agent Clip Layer DOP, so select First Trigger Input from the drop-down menu.

The final animation of the agents clapping when they are inside the bounding box:

The setup of the object and SOP-level networks is similar to the previous example, but now, we have the addition of setting up the layered clip to be a difference clip:

1. For the parameters to set on the Agent SOP, see the previous example.

2. Add the base (walking) animation clip to the agent definition using the first Agent Clip SOP, add_clips. See the previous example for the parameters to set.

3. Add the head turning clip to the agent definition using the same Agent Clip SOP, add_clips:

   • Click beside Clips to add another set of clip parameters.

   • Set Name to head_turn.

   • Set Character Rig to ../../head_turn.

   • Delete the channels on Start/End/Inc - Start/End/Inc and select Delete Channels.

   • On Start/End/Inc, set the start and end frames of the walking clip.

4. Set up the difference clip.

5. For the parameters to set on the Agent Transform Group SOP, see the previous example.

6. We only want to see one agent in the crowd, so on the Crowd Source SOP:

   • Set Layout to Formation.

   • Set Rows and Columns to 1.

   • Set Initial State to walk.

7. Set up the DOP simulation network.

1. Set up the CHOP network to create the difference clip:

   

2. Import the head turning clip from the agent definition using an Agent CHOP. On the Agent CHOP:

   • Set SOP Path to the SOP node that contains the agent with the clip to import, in our example, ../../add_clips.

   • Set Clip Name to the name of the layered animation clip, in our example, head_turn.

3. On the Pose Difference CHOP, set the frame number of the clip you want to use for the reference pose.

4. In the parent SOP network, add the difference clip to the agent definition using the second Agent Clip SOP, add_difference_clip:

   • Set Input to CHOP.

   • Specify a name for the difference clip in the Name parameter, in our example, head_turn_additive.

   • Set CHOP to the CHOP network output, in our example, ../set_up_difference_clip/HEAD_TURN_ADDITIVE.

   Warning

   If you try to add the difference clip into the Agent Clip SOP that contains the original layered animation, this will result in an error.

The image below displays the DOP network, crowd_simulation, from the parent SOP network:

1. See the previous example for information on setting the parameters in the Crowd Object and Crowd State DOPs.

2. On the Agent Clip Layer DOP, set the head turning difference clip as a layer on top of the base animation:

   • Set Blend Mode to Additive, which adds the effect of the layer clip on top of the base animation.

   • Set Clip Name to the difference clip, in our example, head_turn_additive. This clip name was set in the parent SOP network's Agent Clip SOP, add_difference_clip.

   • Set Transform Group to upper_body.

   • Adjust the Blend Ratio to control the percentage of the layer to add on top of the base animation.

The final animation with the head turning clip layered on top of the walking animation is shown on the right: